The faulty NVIDIA drivers from 10.5.3 have been fixed, if anyone's interested. WoW no longer suffers from the VRAM leak, and 256-colour mode support has been restored so Diablo II can once again be played on Macs with the 8600M without needing to hack the OS. That said, some people have been reporting weird graphics artifacts in WoW after this update, so if you're using the 10.5.2 graphics update drivers to play WoW, you may not want to upgrade just yet.